<template>
    <el-color-picker v-model="theme"
        :predefine="['#409EFF', '#1890ff', '#304156', '#212121', '#11a983', '#13c2c2', '#6959CD', '#f5222d',]"
        class="theme-picker" popper-class="theme-picker-dropdown" />
</template>

<script>
// element-ui version from node_modules
const version = require('element-ui/package.json').version
const ORIGINAL_THEME = '#409EFF' // default color
import { useSettingsStore } from "@/store/modules/settings"
const settingsStore = useSettingsStore();
export default {
    data() {
        return {
            chalk: '', // content of theme-chalk css
            theme: ''
        }
    },
    computed: {
        defaultTheme() {
            return settingsStore.theme
        }
    },
    watch: {
        defaultTheme: {
            handler: function (val, oldVal) {
                this.theme = val
            },
            immediate: true
        },
        async theme(val) {
            await this.setTheme(val)
        }
    },
    created() {
        if (this.defaultTheme !== ORIGINAL_THEME) {
            this.setTheme(this.defaultTheme)
        }
    },

    methods: {
        async setTheme(val) {
            const oldVal = this.chalk ? this.theme : ORIGINAL_THEME
            if (typeof val !== 'string') return
            const themeCluster = this.getThemeCluster(val.replace('#', ''))
            const originalCluster = this.getThemeCluster(oldVal.replace('#', ''))

            const getHandler = (variable, id) => {
                return () => {
                    const originalCluster = this.getThemeCluster(ORIGINAL_THEME.replace('#', ''))
                    const newStyle = this.updateStyle(this[variable], originalCluster, themeCluster)

                    let styleTag = document.getElementById(id)
                    if (!styleTag) {
                        styleTag = document.createElement('style')
                        styleTag.setAttribute('id', id)
                        document.head.appendChild(styleTag)
                    }
                    styleTag.innerText = newStyle
                }
            }

            if (!this.chalk) {
                const url = `https://unpkg.com/element-ui@${version}/lib/theme-chalk/index.css`
                await this.getCSSString(url, 'chalk')
            }

            const chalkHandler = getHandler('chalk', 'chalk-style')

            chalkHandler()

            const styles = [].slice.call(document.querySelectorAll('style'))
                .filter(style => {
                    const text = style.innerText
                    return new RegExp(oldVal, 'i').test(text) && !/Chalk Variables/.test(text)
                })
            styles.forEach(style => {
                const { innerText } = style
                if (typeof innerText !== 'string') return
                style.innerText = this.updateStyle(innerText, originalCluster, themeCluster)
            })

            this.$emit('change', val)
        },

        updateStyle(style, oldCluster, newCluster) {
            let newStyle = style
            oldCluster.forEach((color, index) => {
                newStyle = newStyle.replace(new RegExp(color, 'ig'), newCluster[index])
            })
            return newStyle
        },

        getCSSString(url, variable) {
            return new Promise(resolve => {
                const xhr = new XMLHttpRequest()
                xhr.onreadystatechange = () => {
                    if (xhr.readyState === 4 && xhr.status === 200) {
                        this[variable] = xhr.responseText.replace(/@font-face{[^}]+}/, '')
                        resolve()
                    }
                }
                xhr.open('GET', url)
                xhr.send()
            })
        },

        getThemeCluster(theme) {
            const tintColor = (color, tint) => {
                let red = parseInt(color.slice(0, 2), 16)
                let green = parseInt(color.slice(2, 4), 16)
                let blue = parseInt(color.slice(4, 6), 16)

                if (tint === 0) { // when primary color is in its rgb space
                    return [red, green, blue].join(',')
                } else {
                    red += Math.round(tint * (255 - red))
                    green += Math.round(tint * (255 - green))
                    blue += Math.round(tint * (255 - blue))

                    red = red.toString(16)
                    green = green.toString(16)
                    blue = blue.toString(16)

                    return `#${red}${green}${blue}`
                }
            }

            const shadeColor = (color, shade) => {
                let red = parseInt(color.slice(0, 2), 16)
                let green = parseInt(color.slice(2, 4), 16)
                let blue = parseInt(color.slice(4, 6), 16)

                red = Math.round((1 - shade) * red)
                green = Math.round((1 - shade) * green)
                blue = Math.round((1 - shade) * blue)

                red = red.toString(16)
                green = green.toString(16)
                blue = blue.toString(16)

                return `#${red}${green}${blue}`
            }

            const clusters = [theme]
            for (let i = 0; i <= 9; i++) {
                clusters.push(tintColor(theme, Number((i / 10).toFixed(2))))
            }
            clusters.push(shadeColor(theme, 0.1))
            return clusters
        }
    }
}
</script>

<style>
.theme-message,
.theme-picker-dropdown {
    z-index: 99999 !important;
}

.theme-picker .el-color-picker__trigger {
    height: 26px !important;
    width: 26px !important;
    padding: 2px;
}

.theme-picker-dropdown .el-color-dropdown__link-btn {
    display: none;
}
</style>
